Orthodontic bracket debonding: risk of enamel fracture.

ABSTRACT

OBJECTIVES: Until now, it is not clear if various procedures of bracket debonding differ with regard to their risk of enamel fracture. Therefore, the objective of the present study was to compare these procedures biomechanically for assessing the risk of complications. MATERIALS AND METHODS: An anisotropic finite element method (FEM) model of the mandibular bone including periodontal ligament, enamel, dentin, and an orthodontic bracket was created. The morphology based on the CT data of an anatomical specimen. Typical loading conditions were defined for each method of bracket debonding (compression, shearing off, twisting off). Shortly before the adhesive's break, the induced stress in enamel, periodontal ligament, and in the alveolar bone was measured. The statistical analysis of the obtained values was performed in SPSS 19.0. RESULTS: Relatively high stresses occurred in the enamel using frontal torque (max. 44.18 MPa). With shearing off, the stresses were also high (max. 41.96 MPa), and additionally high loads occurred on the alveolar bone as well (max. 11.79 MPa). Moderate maximum values in enamel and alveolar bone appeared during the compression of the bracket wings (max. 37.12 MPa) and during debonding by lateral torque (max. 35.18 MPa). CONCLUSIONS: The present simulation results indicate that the risk of enamel fracture may depend on the individual debonding procedure. Further clinical trials are necessary to confirm that. CLINICAL RELEVANCE For patients with prior periodontal disease or loosened teeth, a debonding procedure by compression of the bracket wings is recommended, since here the load for the periodontal structures of the tooth is lowest.